Styrene polymer foam and the preparation thereof

Abstract

Stable medium density large cell size styrene polymer foam is extruded in large sections employing as blowing agents: chlorofluoromethane, bromochlorodifluoromethane alone or in admixture with minor quantities of other halogen containing carbon compounds to provide machinable foams of good dimensional stability.

What is claimed is: 
     
       1. An alkenyl aromtic thermoplastic synthetic resinous elongate foam body having a machine direction and a transverse direction, the body defining a plurality of closed noninterconnecting gas containing cells therein, the cells having an average cell size of from about 1.2 to 3 millimeters, the foam body being a generally uniform cellular structure and being without discontinuities, being without substantial variation in average cell size when cell size is measured by averaging cell diameter across the minimum cross-sectional dimension of the body, the elongate body having a cross-sectional area of at least 18 square inches and having a minimum cross-sectional dimension of at least one inch, the foam body having a water vapor permeability not greater than 1.8 perm inches, a density of from about 1.4 to about 5 pounds per cubic foot the body being a continuous hardened thermoplastic gel with the further limitation that the cells contain a blowing agent having as a major component thereof at least 70 weight percent of a member selected from the group consisting of chlorofluoromethane, bromochlorodifluoromethane, and mixtures thereof. 
     
     
       2. The foam body of claim 1 wherein the average cell size is from about 1.4 to 2.6 millimeters. 
     
     
       3. The foam body of claim 1 wherein the blowing agent comprises chlorofluoromethane. 
     
     
       4. The body of claim 1 wherein the blowing agent comprises bromochlorodifluoromethane. 
     
     
       5. The body of claim 1 wherein the alkenyl aromatic synthetic resinous body comprises polystyrene. 
     
     
       6. The body of claim 1 wherein the blowing agent is selected from the group consisting of: a. 75-100% Chlorofluoromethane/0-25% 1,1-Difluoro-1-chloroethane   b. 75-100% Chlorofluoromethane/0-25% Chlorodifluoromethane   c. 85-100% Chlorofluoromethane/0-15% 1,1-Difluoroethane   d. 75-100% Chlorofluoromethane/0-25% Dichlorodifluoromethane   e. 70-100% Chlorofluoromethane/0-30% Bromochlorodifluoromethane   f. 75-100% Chlorofluoromethane/0-25% Dichlorotetrafluoroethane and mixtures thereof.   
     
     
       7. A foamed polystyrene elongate body having a machine direction and a transverse direction, the body defining a plurality of closed noninterconnecting gas containing cells therein, the cells having an average cell size of from about 1.2 to 3 millimeters, the foamed body being a generally uniform cellular structure, being without discontinuities, being without substantial variations in average cell size when cell size is measured by average cell diameter across the minimum cross-sectional dimension of the body, the body having a cross-sectional area of at least 18 square inches and having a minimum cross-sectional dimension of at least one inch, the body having a water vapor permeability not greater than 1.8 perm inches, a density of from about 1.4 to 5 pounds per cubic foot the body being a continuous hardened thermoplastic gel with the further limitations that the cells contain a blowing agent having a major component thereof at least 70 weight percent of a member selected from the group consisting of chlorofluoromethane, bromochlorodifluoromethane, and mixtures thereof. 
     
     
       8. The foam body of claim 7 wherein the average cell size is from about 1.4 to 2.6 millimeters. 
     
     
       9. The foam body of claim 7 wherein the blowing agent comprises chlorofluoromethane. 
     
     
       10. The body of claim 7 wherein the blowing agent comprises bromochlorodifluoromethane. 
     
     
       11. The body of claim 7 wherein the alkenyl aromatic synthetic resinous body comprises polystyrene. 
     
     
       12. The body of claim 7 wherein the blowing agent is selected from the group consisting of: a. 75-100% Chlorofluoromethane/0-25% 1,1-Difluoro-1-chloroethane   b. 75-100% Chlorofluoromethane/0-25% Chlorodifluoromethane   c. 85-100% Chlorofluoromethane/0-15% 1,1-Difluoroethane   d. 75-100% Chlorofluoromethane/0-25% Dichlorodifluoromethane   e. 70-100% Chlorofluoromethane/0-30% Bromochlorodifluoromethane   f. 75-100% Chlorofluoromethane/0-25% Dichlorotetrafluoroethane and mixtures thereof.